1. Field of the Invention
The present invention relates to a portable transmitter, which is advantageously used as a transmitter in a keyless-entry system for an automobile and in a keyless-starter system.
2. Description of Related Art
In conventional transmitters of this kind, a transponder for wirelessly transmitting an identification code (ID code) to a device to be operated is contained in a case. In a keyless-starter system for an automobile, for example, the engine is permitted to start when an IC code sent form the transmitter coincides with an ID code pre-installed in the automobile.
An example of the transmitter of this kind is disclosed in JP-A-2001-140513. A case containing components of the transmitter including a transponder and a battery is composed of a front case and a rear case, both being detachably connected. To replace a worn battery with a new one, it is necessary to be able to easily open the case. The case structure having the front case and the rear case detachably connected to each other, however, involves the following problem. The case may be opened by an unauthorized person such as a thief, and the transponder may be stolen without leaving a trace that the case was opened by someone. The thief is able to start the engine using the transponder to steal the automobile. Since no trace showing such an unauthorized act is left, it is highly possible that the owner does not notice for a certain period of time that the transponder is taken out from the transmitter case. Therefore, the possibility that the automobile is stolen will increase. The same problem is involved in the keyless-entry system.